#include <stdio.h>
#include <ctype.h>
#include <math.h>

#define MAXOP 100
#define NUMBER '0'
#define NAME 'n'
#define MAXVAL 100
#define MAXLINE 100
#define PI 3.14159265358979323846

int sp=0;
double val[MAXVAL];
int li=0;
char line[MAXLINE];

int getop(char []);
void push(double);
double pop(void);
void mathfnc(char []);
int getline(char line[],int limit);

main()
{
 int i,type,var=0;
 double op1,op2;
 char s[MAXOP];
 double variable[26];
 
 for (i=0;i<26;i++)
  variable[i]=0.0;
 while ((type=getop(s)) != EOF) {
  switch (type) {
  case NUMBER:
   push(atof(s));
   break;
  case NAME:
   mathfnc(s);
   break;
  case '+':
   push(pop()+pop());
   break;
  case '-':
   op2=pop();
   push(pop()-op2);
   break;
  case '*':
   push(pop()*pop());
   break;
  case '/':
   op2=pop();
   if (op2 != 0.0)
    push(pop() / op2);
   else
    printf("error: zero divisor\n");
   break;
  case '%':
   op2=pop();
   if (op2!=0.0)
    push(fmod(pop(),op2));
   else
    printf("error: zero divisor\n");
   break;
  case '=':
    pop();
    if (var>='A' && var<='Z')
     variable[var - 'A']=pop();
    else
     printf("error: no variable name\n");
    break;
  case 'q':
   exit (0);
  case '\n':
   printf("\t%.8g\n",pop());
   break;
  case '?':
   op2=pop();
   printf("\t%.8g\n",op2);
   push(op2);
   break;
  default:
    printf("error: unknown command %s\n",s);
    break;
  }
 }
 return 0;
}

int getline(char s[],int lim)
{
 int c,i;
 
 i=0;
 while (--lim > 0 && (c=getchar()) != EOF && c !='\n')
  s[i++]=c;
 if (c=='\n')
  s[i++]=c;
 s[i]='\0';
 return i;
}

void push(double f)
{
 if (sp<MAXVAL)
  val[sp++]=f;
 else
  printf("error: stack fll,can't push %g\n",f);
}

double pop(void)
{
 if (sp>0)
  return val[--sp];
 else {
  printf("error: stack empty\n");
  return 0.0;
 }
}

int getop(char s[])
{
 int c,i;
 
 if (line[li]=='\0')
  if (getline(line,MAXLINE)==0)
   return EOF;
  else
   li=0;
 
 while ((s[0]=c=line[li++])==' ' || c=='\t')
  ;
 s[1]='\0';
 i=0;
 if (islower(c)) {
  while (islower(s[++i] = c = line[li++]))
   ;
  s[i]='\0';
  if (strlen(s)>1)
   return NAME;
  else
   return c;
 }
 
 if (!isdigit(c) && c!='.')
  return c;
 if (isdigit(c))
  while (isdigit(s[++i]=c=line[li++]))
   ;
 if (c=='.')
  while (isdigit(s[++i]=c=line[li++]))
   ;
 s[i]='\0';
 li--;
 return NUMBER;
}

void mathfnc(char s[])
{
 double op2;
 
 if (strcmp(s,"sin")==0)
  push(sin(pop()));
 else if (strcmp(s,"cos")==0)
  push(cos(pop()));
 else if (strcmp(s,"tan")==0)
  push(tan(pop()));
 else if (strcmp(s,"pow")==0) {
  op2=pop();
  push(pow(pop(),op2));
 } else if (strcmp(s,"quit")==0) 
  exit (0);
 else if (strcmp(s,"asin")==0)
  push(asin(pop()));
 else if (strcmp(s,"acos")==0)
  push(acos(pop()));
 else if (strcmp(s,"atan")==0)
  push(atan(pop()));
 else if (strcmp(s,"cosh")==0)
  push(cosh(pop()));
 else if (strcmp(s,"sinh")==0)
  push(sinh(pop()));
 else if (strcmp(s,"tanh")==0)
  push(tanh(pop()));
 else if (strcmp(s,"exp")==0)
  push(exp(pop()));
 else if (strcmp(s,"log")==0)
  push(log10(pop()));
 else if (strcmp(s,"ln")==0)
  push(log(pop()));
 else if (strcmp(s,"sqrt")==0)
  push(sqrt(pop()));
 else if (strcmp(s,"pi")==0)
  push(PI);
 else if (strcmp(s,"rot")==0)
  push(1 / (pop()));
 else if (strcmp(s,"chs")==0)
  push(-1*pop());
 else
  printf("error: %s not supported\n",s);
}